5 ms·

Face masks for Covid pass their largest test yet

16 points by sohkamyung 5y ago

wrycoder 5y ago
You have to read a footnote in the original paper to understand that the “surgical” masks used actually contained a blown fiber layer, like N95s, and passed the 95% filtration level when tested. These are not the surgical/procedure masks that we see people commonly wearing in the US. Not only that, but they cost thirteen cents apiece. Why don’t we have those in the US? Edit: it’s not a very good trial, because mask compliance was poor in spite of their efforts, and they didn’t separate the mask wearing groups when evaluating the outcomes, though they could have. I would have expected better results from the “surgical” masks. You really have to read the original paper to assess this trial properly.
- criticaltinker 5y ago
  Great points. It’s worth adding that SARS-COV-2 is spread primarily through the air via extremely tiny droplets (< 5 μm) [1]. Breathing, coughing, and sneezing produces infectious aerosols which can remain suspended in the air for hours. Most cloth masks that are used by the general public will provide very little protection against inhaling or producing these aerosols [2], though such masks are likely to help reduce the spread of larger droplets. [1] Airborne transmission of respiratory viruses https://www.science.org/lookup/doi/10.1126/science.abd9149 https://www.science.org/lookup/doi/10.1126/science.abd9149 [2] Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks https://pubs.acs.org/doi/10.1021/acsnano.0c03252# https://pubs.acs.org/doi/10.1021/acsnano.0c03252#
- angelzen 5y ago
  > “surgical” masks used actually contained a blown fiber layer, like N95s, and passed the 95% filtration level when tested. > The study’s authors found that surgical masks — but not cloth masks — reduced transmission of SARS-CoV-2 in villages where the research team distributed face masks and promoted their use. West coast city: 90% of the people I see around wear useless cloth masks. Borders on criminal that we pretend the mask-as-virtue-statement circus we are currently undergoing has any benefit other than reduced oxygen flow.
  - mike00632 5y ago
    We've gone from quoting a part of the article leaving out the part that discusses cloth mask efficacy to full blown denial of what the study concludes about cloth masks, regurgitation tired old anti-mask rhetoric.
    - angelzen 5y ago
      I'm sorry, please help me: where does the study say cloth masks help?
      - mike00632 5y ago
        "Material difference The study linked surgical masks with an 11% drop in risk, compared with a 5% drop for cloth..."
        angelzen 5y ago
        Consider taking it up with Lynne Peeples. The very subtitle of the piece is 'surgical masks are highly protective, but cloth masks fall short', I have no idea why she thinks '11% drop in risk' is 'highly protective', but '5% drop' is 'falling short'. Either way the numbers appear marginal at best. Edit: Fundamentally I have an issue with any definition of risk that bounds the measure to a short time frame. For all we know the mask intervention may slow the spread speed by a small factor, but were we to measure over a year (or even longer) we might observe the same total number of infections: the virus is going to infect everyone susceptible, only at a slightly slower pace.
        mike00632 5y ago
        1. Based on the size of the study there are thresholds for statistical significance. 2. Only a portion of the people were even wearing masks. A few people wore masks and the risk of infection dropped by a few percent. Declaring masks don't work because a couple people wore them yet the entire population didn't see a complete decline in infection is illogical and dishonest. 3. The study not being able to conclude in a statistically significant way that cloth masks prevent infection is completely different from concluding that cloth masks are worthless. Your aversion to masks is completely a reflection of your bias and not supported by this study.
- abdullahkhalids 5y ago
  The other important piece of information in that footnote is that filtration efficiency of cloth masks depend highly on their material and design. I wish it was possible to actually test the filtration efficiency of cloth and surgical masks available in the market.
hamburgerwah 5y ago
Anyone who has actually read even the first few pages of the so called "gold standard" study cited knows it was useless and inapplicable to any meaningful public health practice. But the narrative MUST NOT BE deviated from. I don't think we as a modern civilization will recover for a hundred years from the way in which institutions like nature have debased themselves with political pandering.
- deleted 5y ago
  [deleted]
suyula 5y ago
> Neither the laboratory findings nor the mask-trial findings have been peer reviewed. Then why are Nature reporting on them in such conclusive language?
- angelzen 5y ago
  Because they believe the best way to preserve their careers is to regurgitate official dogma. It becomes an absurd race of who's performing this ritual in the strongest possible terms. It's going to get worse, keep an eye for explicit adulation of the wisdom of the political authorities. If there is any Russian speaker around, would be instructive to take one of the old top Soviet science publications and translate the TOC.
- HWR_14 5y ago
  >> Neither the laboratory findings nor the mask-trial findings have been peer reviewed. > Then why are Nature reporting on them in such conclusive language? Given Nature has very well-regarded peer reviewers, it seems likely that this is an earlier report on something they expect to publish as peer reviewed. Why report it now? Because people are dying and this could help them. Are they arguing over comma locations? Waiting until the next publication date? Who knows.
timr 5y ago
The actual paper: https://www.poverty-action.org/sites/default/files/publications/Mask_RCT____Symptomatic_Seropositivity_083121.pdf https://www.poverty-action.org/sites/default/files/publicati... The study found an effect size of zero in the cloth mask cohort, and an 11% difference in the surgical mask cohort. Effect sizes that managed significance were just barely significant, at a p-value of 0.043. Also, the researchers didn't do any baseline serology, so it's quite difficult to know if there was a starting bias influencing the final results. It's also difficult to know the degree to which the non-blinded nature of the study and voluntary seroprevalence testing biased the outcome. At such small effect sizes, questions like these matter a great deal. Nevertheless, it is encouraging that someone actually bothered to do a proper RCT of masking as "protection for others", and this study has several points that should be widely communicated (e.g. the ineffectiveness of cloth masks). However, I would not say that "masks passed their test" is really one of them...these results are pretty mediocre. Vinay Prasad of UCSF has made an excellent summary of the results of the Bangladesh RCT, and I recommend it strongly: https://twitter.com/VPrasadMDMPH/status/1435679462142607361 https://twitter.com/VPrasadMDMPH/status/1435679462142607361

16 points by sohkamyung 5y ago

You have to read a footnote in the original paper to understand that the “surgical” masks used actually contained a blown fiber layer, like N95s, and passed the 95% filtration level when tested. These are not the surgical/procedure masks that we see people commonly wearing in the US. Not only that, but they cost thirteen cents apiece. Why don’t we have those in the US? Edit: it’s not a very good trial, because mask compliance was poor in spite of their efforts, and they didn’t separate the mask wearing groups when evaluating the outcomes, though they could have. I would have expected better results from the “surgical” masks. You really have to read the original paper to assess this trial properly.

criticaltinker 5y ago
Great points. It’s worth adding that SARS-COV-2 is spread primarily through the air via extremely tiny droplets (< 5 μm) [1]. Breathing, coughing, and sneezing produces infectious aerosols which can remain suspended in the air for hours. Most cloth masks that are used by the general public will provide very little protection against inhaling or producing these aerosols [2], though such masks are likely to help reduce the spread of larger droplets. [1] Airborne transmission of respiratory viruses https://www.science.org/lookup/doi/10.1126/science.abd9149 https://www.science.org/lookup/doi/10.1126/science.abd9149 [2] Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks https://pubs.acs.org/doi/10.1021/acsnano.0c03252# https://pubs.acs.org/doi/10.1021/acsnano.0c03252#
angelzen 5y ago
> “surgical” masks used actually contained a blown fiber layer, like N95s, and passed the 95% filtration level when tested. > The study’s authors found that surgical masks — but not cloth masks — reduced transmission of SARS-CoV-2 in villages where the research team distributed face masks and promoted their use. West coast city: 90% of the people I see around wear useless cloth masks. Borders on criminal that we pretend the mask-as-virtue-statement circus we are currently undergoing has any benefit other than reduced oxygen flow.
- mike00632 5y ago
  We've gone from quoting a part of the article leaving out the part that discusses cloth mask efficacy to full blown denial of what the study concludes about cloth masks, regurgitation tired old anti-mask rhetoric.
  - angelzen 5y ago
    I'm sorry, please help me: where does the study say cloth masks help?
    - mike00632 5y ago
      "Material difference The study linked surgical masks with an 11% drop in risk, compared with a 5% drop for cloth..."
      - angelzen 5y ago
        Consider taking it up with Lynne Peeples. The very subtitle of the piece is 'surgical masks are highly protective, but cloth masks fall short', I have no idea why she thinks '11% drop in risk' is 'highly protective', but '5% drop' is 'falling short'. Either way the numbers appear marginal at best. Edit: Fundamentally I have an issue with any definition of risk that bounds the measure to a short time frame. For all we know the mask intervention may slow the spread speed by a small factor, but were we to measure over a year (or even longer) we might observe the same total number of infections: the virus is going to infect everyone susceptible, only at a slightly slower pace.
        mike00632 5y ago
        1. Based on the size of the study there are thresholds for statistical significance. 2. Only a portion of the people were even wearing masks. A few people wore masks and the risk of infection dropped by a few percent. Declaring masks don't work because a couple people wore them yet the entire population didn't see a complete decline in infection is illogical and dishonest. 3. The study not being able to conclude in a statistically significant way that cloth masks prevent infection is completely different from concluding that cloth masks are worthless. Your aversion to masks is completely a reflection of your bias and not supported by this study.
abdullahkhalids 5y ago
The other important piece of information in that footnote is that filtration efficiency of cloth masks depend highly on their material and design. I wish it was possible to actually test the filtration efficiency of cloth and surgical masks available in the market.

hamburgerwah 5y ago

Anyone who has actually read even the first few pages of the so called "gold standard" study cited knows it was useless and inapplicable to any meaningful public health practice. But the narrative MUST NOT BE deviated from. I don't think we as a modern civilization will recover for a hundred years from the way in which institutions like nature have debased themselves with political pandering.

deleted 5y ago
[deleted]

suyula 5y ago

> Neither the laboratory findings nor the mask-trial findings have been peer reviewed. Then why are Nature reporting on them in such conclusive language?

angelzen 5y ago
Because they believe the best way to preserve their careers is to regurgitate official dogma. It becomes an absurd race of who's performing this ritual in the strongest possible terms. It's going to get worse, keep an eye for explicit adulation of the wisdom of the political authorities. If there is any Russian speaker around, would be instructive to take one of the old top Soviet science publications and translate the TOC.
HWR_14 5y ago
>> Neither the laboratory findings nor the mask-trial findings have been peer reviewed. > Then why are Nature reporting on them in such conclusive language? Given Nature has very well-regarded peer reviewers, it seems likely that this is an earlier report on something they expect to publish as peer reviewed. Why report it now? Because people are dying and this could help them. Are they arguing over comma locations? Waiting until the next publication date? Who knows.

timr 5y ago

The actual paper: https://www.poverty-action.org/sites/default/files/publications/Mask_RCT____Symptomatic_Seropositivity_083121.pdf https://www.poverty-action.org/sites/default/files/publicati... The study found an effect size of zero in the cloth mask cohort, and an 11% difference in the surgical mask cohort. Effect sizes that managed significance were just barely significant, at a p-value of 0.043. Also, the researchers didn't do any baseline serology, so it's quite difficult to know if there was a starting bias influencing the final results. It's also difficult to know the degree to which the non-blinded nature of the study and voluntary seroprevalence testing biased the outcome. At such small effect sizes, questions like these matter a great deal. Nevertheless, it is encouraging that someone actually bothered to do a proper RCT of masking as "protection for others", and this study has several points that should be widely communicated (e.g. the ineffectiveness of cloth masks). However, I would not say that "masks passed their test" is really one of them...these results are pretty mediocre. Vinay Prasad of UCSF has made an excellent summary of the results of the Bangladesh RCT, and I recommend it strongly: https://twitter.com/VPrasadMDMPH/status/1435679462142607361 https://twitter.com/VPrasadMDMPH/status/1435679462142607361